Decompose on text and icons converts the symbol into a set of polylines. This conversion is not always perfect, and may have left the insides of letters the wrong color, or placed the insides of letters behind other parts of the letter. To correct those problems, try selecting the outermost polygon (hold down Alt and click near its edge). Then use Send to Back to show the inside of the letter. You should be able now to select just the inside polygon and correct the fill color if necessary.